Mount root from SD card?

[M. Warner Losh]

In message: <497748D9.2040607 at FreeBSD.org>
            Alexander Motin <mav at FreeBSD.org> writes:
: Krassimir Slavchev wrote:
: > ...
: > CMD: 7 ARG 0 len 0
: > RES: 0
: 
: Before this point mmc_rescan_cards() have successfully selected all the
: cards. Then at this point
: 	mmcbr_set_bus_mode(dev, pushpull);
: 
:         mmcbr_update_ios(dev);
: were called. And after that same request inside mmc_calculate_clock()
: has failed. That's strange.
: 
: > timing 1, rate 30000000, hsrate 50000000
: > CMD: 7 ARG 10000 len 0
: > RES: 2
: 
: Open drain bus mode control is not implemented by sdhci driver, so I
: haven't looked at it close. Quick look around shows that push-pull mode
: was set there even without that last call. May be I am wrong, but first
: line looks useless. mmcbr_update_ios(dev) writes to the controller bus
: control registers, may be it affects something, or bus require some time
: to settle after it?

Without open drain bus mode, I don't think that you can properly do
MMC cards.  At least I couldn't with the AT91 when I was developing
it.  The open drain mode is what allows us to select the one mmc card
we're talking to.

: > CMD: 6 ARG 80fffff0 len 64
: > RES: 0
: > CMD: 7 ARG 0 len 0
: > RES: 0
: > mmc0: setting transfer rate to 30.000MHz
: > mmcsd0: 1983MB <SD Memory Card> at mmc0 30MHz/1bit
: 
: Bus frequency changed here. SD specification allows frequencies up to
: 25MHz without high speed timings used, but cards like this one ofter
: declare a bit higher frequencies in legacy mode. May be we should just
: to try to limit it to some safe value? You may just try to set
: max_dtr = 5000000;
: in mmc_calculate_clock(), before "if (bootverbose) {".

The AT91 stuff works well in high speed mode, but the internal clocks
of the AT91 may limit it to a number less than 50MHz.  The 30MHz limit
actually should be at91_master_clock / 2, so that's a bit of a bug in
the driver (which I've fixed in my tree).  I've made 30MHz work on the
prior version of the code, so there's not a hardware limitation.

BTW, at91_master_clock is 60,000,000 by default, so we can't go higher
than 30MHz on those boards.

Warner

: > CMD: 7 ARG 10000 len 0
: > RES: 2
: > mmc0: setting bus width to 1 bits
: > CMD: 37 ARG 10000 len 0
: > RES: 0
: > CMD: 6 ARG 0 len 0
: > RES: 0
: > CMD: 11 ARG 0 len 512
: > RES: 0
: > CMD: 11 ARG 0 len 512
: > RES: 0
: > CMD: 11 ARG 200 len 512
: > RES: 0
: > Trying to mount root from ufs:/dev/mmcsd0s1
: > 
: > Alexander Motin wrote:
: >> Krassimir Slavchev wrote:
: >>> Alexander Motin wrote:
: >>>> Krassimir Slavchev wrote:
: >>>>> Oops, sorry this output was without SD card inserted!
: >>>>> I've changed the file.
: >>>> That's some different debugging. I have meant that one, which happens
: >>>> when boot_verbose="YES" added to loader.conf, or respective Fx button
: >>>> pressed during boot on PC.
: >>> Yes this is with kernel VERBOSE_SYSINIT option because I cannot set
: >>> boot_verbose from arm boot loader.
: >>> Verbose messages from which modules you want to see? I will set
: >>> bootverbose manually.
: >> mmc. And while being there, apply this one please.
: 
: -- 
: Alexander Motin
: 
: